kernel/drivers/clk/sunxi/clk-sun6i-ar100.c

   1 /*
   2  * Copyright (C) 2014 Free Electrons
   3  *
   4  * License Terms: GNU General Public License v2
   5  * Author: Boris BREZILLON <boris.brezillon@free-electrons.com>
   6  *
   7  * Allwinner A31 AR100 clock driver
   8  *
   9  */
  10
  11 #include <linux/clk-provider.h>
  12 #include <linux/module.h>
  13 #include <linux/of.h>
  14 #include <linux/platform_device.h>
  15
  16 #define SUN6I_AR100_MAX_PARENTS         4
  17 #define SUN6I_AR100_SHIFT_MASK          0x3
  18 #define SUN6I_AR100_SHIFT_MAX           SUN6I_AR100_SHIFT_MASK
  19 #define SUN6I_AR100_SHIFT_SHIFT         4
  20 #define SUN6I_AR100_DIV_MASK            0x1f
  21 #define SUN6I_AR100_DIV_MAX             (SUN6I_AR100_DIV_MASK + 1)
  22 #define SUN6I_AR100_DIV_SHIFT           8
  23 #define SUN6I_AR100_MUX_MASK            0x3
  24 #define SUN6I_AR100_MUX_SHIFT           16
  25
  26 struct ar100_clk {
  27         struct clk_hw hw;
  28         void __iomem *reg;
  29 };
  30
  31 static inline struct ar100_clk *to_ar100_clk(struct clk_hw *hw)
  32 {
  33         return container_of(hw, struct ar100_clk, hw);
  34 }
  35
  36 static unsigned long ar100_recalc_rate(struct clk_hw *hw,
  37                                        unsigned long parent_rate)
  38 {
  39         struct ar100_clk *clk = to_ar100_clk(hw);
  40         u32 val = readl(clk->reg);
  41         int shift = (val >> SUN6I_AR100_SHIFT_SHIFT) & SUN6I_AR100_SHIFT_MASK;
  42         int div = (val >> SUN6I_AR100_DIV_SHIFT) & SUN6I_AR100_DIV_MASK;
  43
  44         return (parent_rate >> shift) / (div + 1);
  45 }
  46
  47 static long ar100_determine_rate(struct clk_hw *hw, unsigned long rate,
  48                                  unsigned long min_rate,
  49                                  unsigned long max_rate,
  50                                  unsigned long *best_parent_rate,
  51                                  struct clk_hw **best_parent_clk)
  52 {
  53         int nparents = __clk_get_num_parents(hw->clk);
  54         long best_rate = -EINVAL;
  55         int i;
  56
  57         *best_parent_clk = NULL;
  58
  59         for (i = 0; i < nparents; i++) {
  60                 unsigned long parent_rate;
  61                 unsigned long tmp_rate;
  62                 struct clk *parent;
  63                 unsigned long div;
  64                 int shift;
  65
  66                 parent = clk_get_parent_by_index(hw->clk, i);
  67                 parent_rate = __clk_get_rate(parent);
  68                 div = DIV_ROUND_UP(parent_rate, rate);
  69
  70                 /*
  71                  * The AR100 clk contains 2 divisors:
  72                  * - one power of 2 divisor
  73                  * - one regular divisor
  74                  *
  75                  * First check if we can safely shift (or divide by a power
  76                  * of 2) without losing precision on the requested rate.
  77                  */
  78                 shift = ffs(div) - 1;
  79                 if (shift > SUN6I_AR100_SHIFT_MAX)
  80                         shift = SUN6I_AR100_SHIFT_MAX;
  81
  82                 div >>= shift;
  83
  84                 /*
  85                  * Then if the divisor is still bigger than what the HW
  86                  * actually supports, use a bigger shift (or power of 2
  87                  * divider) value and accept to lose some precision.
  88                  */
  89                 while (div > SUN6I_AR100_DIV_MAX) {
  90                         shift++;
  91                         div >>= 1;
  92                         if (shift > SUN6I_AR100_SHIFT_MAX)
  93                                 break;
  94                 }
  95
  96                 /*
  97                  * If the shift value (or power of 2 divider) is bigger
  98                  * than what the HW actually support, skip this parent.
  99                  */
 100                 if (shift > SUN6I_AR100_SHIFT_MAX)
 101                         continue;
 102
 103                 tmp_rate = (parent_rate >> shift) / div;
 104                 if (!*best_parent_clk || tmp_rate > best_rate) {
 105                         *best_parent_clk = __clk_get_hw(parent);
 106                         *best_parent_rate = parent_rate;
 107                         best_rate = tmp_rate;
 108                 }
 109         }
 110
 111         return best_rate;
 112 }
 113
 114 static int ar100_set_parent(struct clk_hw *hw, u8 index)
 115 {
 116         struct ar100_clk *clk = to_ar100_clk(hw);
 117         u32 val = readl(clk->reg);
 118
 119         if (index >= SUN6I_AR100_MAX_PARENTS)
 120                 return -EINVAL;
 121
 122         val &= ~(SUN6I_AR100_MUX_MASK << SUN6I_AR100_MUX_SHIFT);
 123         val |= (index << SUN6I_AR100_MUX_SHIFT);
 124         writel(val, clk->reg);
 125
 126         return 0;
 127 }
 128
 129 static u8 ar100_get_parent(struct clk_hw *hw)
 130 {
 131         struct ar100_clk *clk = to_ar100_clk(hw);
 132         return (readl(clk->reg) >> SUN6I_AR100_MUX_SHIFT) &
 133                SUN6I_AR100_MUX_MASK;
 134 }
 135
 136 static int ar100_set_rate(struct clk_hw *hw, unsigned long rate,
 137                           unsigned long parent_rate)
 138 {
 139         unsigned long div = parent_rate / rate;
 140         struct ar100_clk *clk = to_ar100_clk(hw);
 141         u32 val = readl(clk->reg);
 142         int shift;
 143
 144         if (parent_rate % rate)
 145                 return -EINVAL;
 146
 147         shift = ffs(div) - 1;
 148         if (shift > SUN6I_AR100_SHIFT_MAX)
 149                 shift = SUN6I_AR100_SHIFT_MAX;
 150
 151         div >>= shift;
 152
 153         if (div > SUN6I_AR100_DIV_MAX)
 154                 return -EINVAL;
 155
 156         val &= ~((SUN6I_AR100_SHIFT_MASK << SUN6I_AR100_SHIFT_SHIFT) |
 157                  (SUN6I_AR100_DIV_MASK << SUN6I_AR100_DIV_SHIFT));
 158         val |= (shift << SUN6I_AR100_SHIFT_SHIFT) |
 159                (div << SUN6I_AR100_DIV_SHIFT);
 160         writel(val, clk->reg);
 161
 162         return 0;
 163 }
 164
 165 static struct clk_ops ar100_ops = {
 166         .recalc_rate = ar100_recalc_rate,
 167         .determine_rate = ar100_determine_rate,
 168         .set_parent = ar100_set_parent,
 169         .get_parent = ar100_get_parent,
 170         .set_rate = ar100_set_rate,
 171 };
 172
 173 static int sun6i_a31_ar100_clk_probe(struct platform_device *pdev)
 174 {
 175         const char *parents[SUN6I_AR100_MAX_PARENTS];
 176         struct device_node *np = pdev->dev.of_node;
 177         const char *clk_name = np->name;
 178         struct clk_init_data init;
 179         struct ar100_clk *ar100;
 180         struct resource *r;
 181         struct clk *clk;
 182         int nparents;
 183         int i;
 184
 185         ar100 = devm_kzalloc(&pdev->dev, sizeof(*ar100), GFP_KERNEL);
 186         if (!ar100)
 187                 return -ENOMEM;
 188
 189         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 190         ar100->reg = devm_ioremap_resource(&pdev->dev, r);
 191         if (IS_ERR(ar100->reg))
 192                 return PTR_ERR(ar100->reg);
 193
 194         nparents = of_clk_get_parent_count(np);
 195         if (nparents > SUN6I_AR100_MAX_PARENTS)
 196                 nparents = SUN6I_AR100_MAX_PARENTS;
 197
 198         for (i = 0; i < nparents; i++)
 199                 parents[i] = of_clk_get_parent_name(np, i);
 200
 201         of_property_read_string(np, "clock-output-names", &clk_name);
 202
 203         init.name = clk_name;
 204         init.ops = &ar100_ops;
 205         init.parent_names = parents;
 206         init.num_parents = nparents;
 207         init.flags = 0;
 208
 209         ar100->hw.init = &init;
 210
 211         clk = clk_register(&pdev->dev, &ar100->hw);
 212         if (IS_ERR(clk))
 213                 return PTR_ERR(clk);
 214
 215         return of_clk_add_provider(np, of_clk_src_simple_get, clk);
 216 }
 217
 218 static const struct of_device_id sun6i_a31_ar100_clk_dt_ids[] = {
 219         { .compatible = "allwinner,sun6i-a31-ar100-clk" },
 220         { /* sentinel */ }
 221 };
 222
 223 static struct platform_driver sun6i_a31_ar100_clk_driver = {
 224         .driver = {
 225                 .name = "sun6i-a31-ar100-clk",
 226                 .of_match_table = sun6i_a31_ar100_clk_dt_ids,
 227         },
 228         .probe = sun6i_a31_ar100_clk_probe,
 229 };
 230 module_platform_driver(sun6i_a31_ar100_clk_driver);
 231
 232 MODULE_AUTHOR("Boris BREZILLON <boris.brezillon@free-electrons.com>");
 233 MODULE_DESCRIPTION("Allwinner A31 AR100 clock Driver");
 234 MODULE_LICENSE("GPL v2");